1. Field of the Invention
The present invention relates to the apparatus and method for making electrodeposition blades, and more particularly electrodeposition blades each having same coarseness on its opposite sides.
2. Related Arts
Referring to FIG. 7, cutting means 33 having an electro-deposition blade attached thereto is used in a semiconductor wafer dicing apparatus 30. In dicing a semiconductor wafer W it is 16 attached to a carrier F by means of an adhesive tape T, and the carrier F is sucked on the chuck table 31. Then, the chuck table 31 is moved in an X-direction to be put below the alignment means 32 of the dicing apparatus 30 for detecting the dicing area in the semiconductor wafer W. Then, the chuck table 31 is moved in the X-direction, thereby allowing the cutting means 33 to cut the semiconductor wafer W.
Referring to FIG. 8, the cutting means 33 comprises a spindle unit 35 having an electrodeposition blade 34 attached thereto, a blade monitor 36 for detecting cracks breaking, if any in the blade and a coolant supply 37 for supplying the blade with cooling water.
Referring to FIG. 9, the spindle unit 35 includes a spindle 39 rotatably supported in its housing 38, and a mount flange 40 which is fastened to the tip of the spindle 39 with an associated nut 44. A washer-like electrodeposition blade 41 is sandwiched between the mount flange 40 and the counter flange 42 to be fastened with a blade locking nut 43.
A semiconductor wafer W can be cut with the electrodeposition blade 41 when the spindle 39 is rotated. FIG. 10 shows a similar spindle unit 35 having a hub-like electrodeposition blade 45 attached thereto.
Washer-like electrodeposition blades such as shown in FIG. 9 can be made by an apparatus for making electrodeposition blades as shown in FIG. 11. As shown, an electrolytic cell 15 contains an electrolyte 11 such as nickel sulfate in which pulverized grindstone such as pulverized diamond is suspended. In the electrolyte bath an electrodeposition object 51 and an electrolytic metal 17 such as nickel are immersed, and the electrodeposition object 51 is connected to the minus terminal of an electric source 16 whereas the electrolytic metal 17 is connected to the plus terminal of the electric source 16.
In making a washer-like electrodeposition blade a ring-like object 51 is used as shown in FIG. 12. It is made of aluminum, and its inner and outer circumferences 52 and 53 are covered with masking material, thus leaving its flat annular surfaces 54 to be exposed.
When a predetermined voltage is applied between the electrolytic plate 17 and the electrodeposition object 51, pulverized diamond 12 and ionized metal particles are deposited on the exposed surfaces 54 of the electrodeposition object 51, thus allowing an electro-deposit 55 of pulverized diamond 12 and metal particles to grow thereon.
When the composite layer 55 has reached a desired thickness, the electrodeposition object 13 having the composite layer 55 formed on its surface 54 is taken out from the electrolyte bath 11, and then, the composite layer 55 is removed from the electrodeposition object 51. Thus, the washer-like electrodeposition blade 41 (FIG. 9) results.
As seen from the enlarged fragment view of FIG. 11, the surface 54 of the electrodeposition object 51 on which an electo-deposit is formed is flat, and therefore, the resultant electrodeposition blade 41 has a flat surface formed on one side, on which electrodeposition was started, as indicated by dot-and-dash lines in FIG. 13. In contrast, particles of pulverized grindstone 12 project significantly on the other surface 57 of the electrodeposition blade 41, on which electrodeposition was finished. When a selected workpiece is cut with such electrodeposition blade whose opposite surfaces have different degrees of coarseness, one surface of the workpiece on which it was cut with the less-coarse surface of the electrodeposition blade is different significantly in appearance or physical characteristics from the other surface on which the workpiece was cut with the coarse surface of the electrodeposition blade.
In order to make the deposition-starting surface 56 as coarse as the deposition-finishing surface 57 of the electrodeposition blade it is necessary to effect another electrodeposition on the deposition-starting surface 56 of the resultant electrodeposition blade or to effect etching on the deposition-starting surface 56 to the depth as indicated by dot-and-dash lines 58, thereby exposing as much particulate projections as on the other surface 57. Disadvantageously such extra processing lowers the efficiency with which electrodeposition blades can be made.
There has been, therefore, an increasing demand for facilitating the producing of both coarse-sided electrodeposition blades.